Lightly doped wells are used in various body regions of high voltage semiconductor devices to get high breakdown voltage, while highly doped wells are used in various body regions of low voltage semiconductor devices to lower the resistance. Generally speaking, semiconductor devices with highly doped well as the body region have higher threshold voltage, while semiconductor devices with lightly doped well as the body region have lower threshold voltage. So to make a high voltage semiconductor device, most of BCD (Bipolar-CMOS-DMOS) technologies use lightly doped well with a first doping type as the body region and add an additional layer to adjust the threshold voltage to ensure that the high voltage semiconductor device has a consistent threshold with the low voltage semiconductor device, which increases cost.
Another prior technology uses lightly doped well with a second doping type as the drain region and use low voltage well with the first doping type as the body region. In this case, the threshold voltage adjust layer is not needed, but still an additional well with the second doping type is required, which also increases cost.